Prevention and control of wildlife damage to yards, gardens and landscaping is an age old problem. As the population of deer in many areas is increasing, the damage they cause is also increasing. The magnitude of the problem is indicated by the many types of devices and methods that have been used in attempts to discourage marauding deer.
The ultimate barrier against deer is a woven-wire perimeter fence eight feet tall, but this solution is expensive and unsightly and may violate some zoning ordinances or restrictive covenants.
Natural and chemical repellents are available which can be odor repellents to treat the area, or contact repellents to make the plants taste bad. Many chemicals such as denatonium benzoate and thiram have been tried, as well as mixtures of chemicals with hot sauce, eggs, and glue as in U.S. Pat. No. 4,965,070 (1990) and U.S. Pat. No. 5,183,661 to Messina (1993). Natural remedies have been tried such as extracts of the African Marigold as shown in U.S. Pat. No. 5,554,377 to Abraham (1996). Also touted as animal repellents are coyote urine, lion feces, fermented blood, shredded deodorant soap, garlic, feather meal, cat feces, moth balls, creosote and bags of human hair. These repellents are of questionable efficacy, they require constant reapplication, are malodorous and many chemicals are toxic.
U.S. Pat. No. 5,009,192 to Burman (1991) and U.S. Pat. No. 5,458,093 to MacMillan (1995) show animal repellent devices that suddenly spray water when activated by a motion sensor or an infrared sensor. These devices require connections such as a 110 volt supply, compressed air and a high pressure water supply to operate. These devices would not be useful in sub-freezing temperatures and they would be a surprise for the gardener if they were not disarmed when she went to work in the garden.
Scarecrows, strobe lights and noise making devices such as propane exploders, fireworks, sirens and gunfire have been used to deter deer. U.S. Pat. No. 3,799,105 to Porter (1974) and U.S. Pat. No. 5,148,621 to Rosen (1992) show complicated mechanical devices intended to act as scarecrows by the sights and sounds that they produce. Both of these devices require a 110 volt power supply. Another deer scarecrow with provisions for scent and sound making means is shown by U.S. Pat. No. 4,890,571 to Gaskill (1990). Noise making devices such as these are very annoying to nearby humans, especially at night which is when the deer are most likely to be around. Noise making devices and scarecrows have proven to be ineffective because deer are intelligent and soon realize that this type of device will not harm them.
Ultrasonic animal repellents have been described. U.S. Pat. No. 4,566,085 to Weinberg (1986) and U.S. Pat. No. 5,602,523 to Turchioe (1997) describe devices that produces ultrasound of varying frequencies. As with scarecrows, deer soon learn that these devices are of no threat to them.
Deer are intelligent animals and they soon learn to ignore most deterrent devices. The exception to this are repellent and training devices which deliver an electric shock. Use of shock producing devices has been shown to result in immediate retreat and learned avoidance behaviors. Many shock-producing animal training devices are dependent upon placing a collar on the animal and so are of no value in dealing with wild animals. Another type of device is shown by U.S. Pat. No. 2,579,178 to Dierking (1951) with a shocking apparatus powered by the spark plug of a gasoline engine. An animal carcass such as a rabbit is electrified to train dogs to avoid this type of animal. This device produces whole body shocks and would not be practical as a deer repellent device. U.S. Pat. No. 4,153,009 to Boyle (1979) shows a device to provide a continuous direct current to an animal chewing on a bandage. The low voltage of this device, 9-69 volts direct current, comes directly from the batteries. While this device provides a mild irritant to a dog chewing on a bandage, it does not provide the sharp, powerful stimulus required to be effective as a wild animal deterrent. U.S. Pat. No. 4,476,810 to Heras (1984) shows a dog training device which requires the animal to bite an electrified steak in a precise way to close the circuit and deliver a continuous electric shock which consists of a pulsating direct current. U.S. Pat. No. 4,630,571 to Palmer (1986) shows a device to repel animals which involves a high resistance circuit passing through the body and feet of the target animal and which depends upon the moisture of the earth to conduct the 12 volt direct current used in this device.
Other electrically powered, baited animal extermination devices such as shown by U.S. Pat. No. 922,377 to Ames (1909), French Patent 440,270 to Calvert (1912), Swiss Patent 82,560 to Baumann (1919) and U.S. Pat. No. 5,095,646 to Bunkers (1992) are powered by alternating current or a current from a battery and a converter that is powerful enough to kill the intended victim. These devices would be far too dangerous to openly deploy around a yard or garden and they require a connection to an AC power source or a large battery to maintain such a high voltage and amperage.
Gardeners have found that, other than a tall perimeter fence, the most effective devices now available to protect their gardens from deer and other pests are electric fences or electric meshes. Modern fence charging devices are shown by U.S. Pat. No. 3,900,770 to Kaufman (1975), U.S. Pat. No. 4,394,583 to Standing (1983), U.S. Pat. No. 5,381,298 to Shaw (1995) and U.S. Pat. No. 5,514,919 to Walley (1996). Although these devices incorporate large capacitors which serve to stabilize the output of the device, or which discharge through output transformers to provide an extremely high voltage, none of these devices suggest the device of the present invention and all of these devices require a 120 volt AC power source or a large automobile type battery.
To protect yards and gardens, electric fences that are baited with an attractant such as peanut butter have been shown to be especially effective. Other types of baited electric fence devices are shown by U.S. Pat. No. 3,747,897 to Conley (1973) which combines a noxious repellent with an electric shock to repel predators of livestock, and by U.S. Pat. No. 5,369,909 to Murphy (1994) which shows a bait-holding addition to an electric fence to kill insects.
Electric fences, baited or not, have the problems of being unsightly, expensive, difficult to work around and somewhat permanent. In addition, electric fences produce dangerous whole-body shocks, the amperage and voltage are very high because of the high resistance circuit, and the shock produced is continuous pulses, all of which increase the chance of health problems for an accidental victim with this type of device.